In document WO 2006/054210, a system is disclosed for promoting relaxation by controlling the reproduction of audio/video signals based on the determination of a transition between the different sleep phases. In such a system, periodic sounds generated by physiological characteristics, such as heart rate or breathing rate, are acoustically detected by electro-acoustic sensors. Due to the presence of these sensors that can detect any noise or sound in the room where the monitored person is located, the system requires means for differentiating the different acoustic signals to be detected. However, the control of the reproduction of audio/video signals may be not sufficiently accurate because of environmental noise not caused by the heart or by respiration.